Downregulation Of Dicer Research Articles

Rapid downregulation of DICER is a hallmark of adipose tissue upon high-fat diet feeding

Adipose tissue regulates whole-body energy balance and is crucial for metabolic health. With energy surplus, adipose tissue expands, which may lead to local areas of hypoxia and inflammation, and consequently impair whole-body insulin sensitivity. We report that DICER, a key enzyme for miRNA maturation, is significantly lower in abdominal subcutaneous white adipose tissue of men with obesity compared with men with a lean phenotype. Furthermore, DICER is profoundly downregulated in mouse adipose tissue and liver within the first week on a high-fat diet (HFD), and remains low after prolonged HFD feeding. Downregulation of DICER in mice occurs in both mature adipocytes and stromal vascular cells. Mechanistically, chemically induced hypoxia in vitro shows DICER degradation via interaction with hypoxia-inducible factor 1-α (HIF1α). Moreover, DICER and HIF1α interact in brown adipose tissue post-HFD which may signal for DICER degradation. Finally, RNA sequencing reveals a striking time-dependent downregulation of total miRNA content in mouse subcutaneous adipose tissue after HFD feeding. Collectively, HFD in mice reduces adipose tissue DICER, likely due to hypoxia-induced interaction with HIF1α during tissue expansion, and significantly impacts miRNA content.

MiRNome targeting NF-κB signaling orchestrates macrophage-triggered cancer metastasis and recurrence

Whether and how tumor intrinsic signature determines macrophage-elicited metastasis remain elusive. Here, we show, in detailed studies of data regarding 7,477 patients of 20 types of human cancers, that only 13.8%± 2.6%/27.9%± 3.03% of patients with high macrophage infiltration index exhibit early recurrence/vascular invasion. In parallel, although macrophages enhance the motility of various hepatoma cells, their enhancement intensity is significantly heterogeneous. We identify that the expression of malignant Dicer, a ribonuclease that cleaves miRNA precursors into mature miRNAs, determines macrophage-elicited metastasis. Mechanistically, the downregulation of Dicer in cancer cells leads to defects in miRNome targeting NF-κB signaling, which in turn enhances the ability of cancer cells to respond to macrophage-related inflammatory signals and ultimately promotes metastasis. Importantly, transporting miR-26b-5p, the most potential miRNA targeting NF-κB signaling in hepatocellular carcinoma, can effectively reverse macrophage-elicited metastasis of hepatoma invivo. Our results provide insights into the crosstalk between Dicer-elicited miRNome and cancer immune microenvironments and suggest that strategies to remodel malignant cell miRNome may overcome pro-tumorigenic activities of inflammatory cells.

DICER activates autophagy and promotes cisplatin resistance in non-small cell lung cancer by binding with let-7i-5p

ObjectiveDrug resistance is the main obstacle in the treatment of non-small cell lung cancer (NSCLC). This study aimed to explore the mechanism of DICER in NSCLC resistance and its downstream signaling pathways. MethodsThe A549 cisplatin (DDP)-resistant strain A549/DDP was established. A549/DDP cells were transfected with DICER- and let-7i-5p-related vectors, and treated with autophagy activator rapamycin. The cell viability and apoptosis were tested by CCK-8 assay and flow cytometry, respectively. The formation of autophagosomes was observed with a transmission electron microscopy. RT-qPCR and Western blot assay were conducted to detect expression levels of DICER, let-7i-5p, autophagy-related proteins, and the PI3K/AKT/mTOR pathway-related proteins. The dual luciferase reporter gene assay was implemented to confirm the targeted binding of DICER and let-7i-5p. ResultsDICER was highly expressed in DDP-resistant NSCLC tissues and cells, and DICER could target and negatively regulate the expression of let-7i-5p. DDP treatment could inhibit the viability and promote cell apoptosis of A549/DDP cells. Downregulation of DICER in A549/DDP cells exhibited a decrease of cell viability, a decreased ratio of LC3-II/LC3-I and autophagosomes, together with an elevation of cell apoptosis rate and the phosphorylation levels of PI3K/AKT/mTOR. Treatment of rapamycin and let-7i-5p inhibitor reversed the effects of downregulated DICER in cell viability, ratio of LC3-II/LC3-I, autophagosomes, cell apoptosis rate and the phosphorylation levels of PI3K/AKT/mTOR in A549/DDP cells. ConclusionOur research suggests that DICER promotes autophagy and DDP resistance in NSCLC through downregulating let-7i-5p, and inhibits the activation of PI3K/AKT/mTOR pathway.

Dicing the Disease with Dicer: The Implications of Dicer Ribonuclease in Human Pathologies.

Gene expression dictates fundamental cellular processes and its de-regulation leads to pathological conditions. A key contributor to the fine-tuning of gene expression is Dicer, an RNA-binding protein (RBPs) that forms complexes and affects transcription by acting at the post-transcriptional level via the targeting of mRNAs by Dicer-produced small non-coding RNAs. This review aims to present the contribution of Dicer protein in a wide spectrum of human pathological conditions, including cancer, neurological, autoimmune, reproductive and cardiovascular diseases, as well as viral infections. Germline mutations of Dicer have been linked to Dicer1 syndrome, a rare genetic disorder that predisposes to the development of both benign and malignant tumors, but the exact correlation of Dicer protein expression within the different cancer types is unclear, and there are contradictions in the data. Downregulation of Dicer is related to Geographic atrophy (GA), a severe eye-disease that is a leading cause of blindness in industrialized countries, as well as to psychiatric and neurological diseases such as depression and Parkinson’s disease, respectively. Both loss and upregulation of Dicer protein expression is implicated in severe autoimmune disorders, including psoriasis, ankylosing spondylitis, rheumatoid arthritis, multiple sclerosis and autoimmune thyroid diseases. Loss of Dicer contributes to cardiovascular diseases and causes defective germ cell differentiation and reproductive system abnormalities in both sexes. Dicer can also act as a strong antiviral with a crucial role in RNA-based antiviral immunity. In conclusion, Dicer is an essential enzyme for the maintenance of physiology due to its pivotal role in several cellular processes, and its loss or aberrant expression contributes to the development of severe human diseases. Further exploitation is required for the development of novel, more effective Dicer-based diagnostic and therapeutic strategies, with the goal of new clinical benefits and better quality of life for patients.

Impaired microRNA processing in neutrophils from rheumatoid arthritis patients confers their pathogenic profile. Modulation by biological therapies.

The aim of this study was to investigate the microRNA (miRNA) expression pattern in neutrophils from rheumatoid arthritis (RA) patients and its contribution to their pathogenic profile and to analyze the effect of specific autoantibodies or inflammatory components in the regulation of miRNA in RA neutrophils and its modulation by biological therapies. Neutrophils were isolated from paired peripheral blood (PB) and synovial fluid samples of 40 patients with RA and from PB of 40 healthy donors. A miRNA array was performed using nCounter technology. Neutrophils from healthy donors were treated in vitrowith antibodies to citrullinated protein antigens isolated from RA patients and tumor necrosis factor-a (TNF-a) or interleukin-6. A number of cytokines and chemokines were analyzed. In vitro treatments of RA-neutrophils with tocilizumab or infliximab were carried out. Transfections with pre-miRNA and DICER downregulation experiments were further performed. RA-neutrophils showed a global downregulation of miRNA and genes involved in their biogenesis, alongside with an upregulation of various potential mRNA targets related to migration and inflammation. Decreased levels of miRNA and DICER correlated with autoimmunity, inflammation and disease activity. Citrullinated protein antigens and TNF-a decreased the expression of numerous miRNA and their biogenesis-related genes, increasing their potential mRNA targets. Infliximab reversed those effects. Transfections with pre-miRNA-223, -126 and -148a specifically modulated genes regulating inflammation, survival and migration whereas DICER depletion influenced the inflammatory profile of neutrophils. Taken together RA-neutrophils exhibited a global low abundance of miRNA induced by autoantibodies and inflammatory markers, which potentially contributed to their pathogenic activation. miRNA biogenesis was significantly impaired in RAneutrophils and further associated with a greater downregulation of miRNA mainly related to migration and inflammation in synovial fluid neutrophils. Finally, anti-TNF-a and anti-interleukin-6 receptor treatments can modulate miRNA levels in the neutrophils, minimizing their inflammatory profile.

Abstract 4301: Hypoxia-induced Nur77 activates PI3K-p110a/Akt/mTOR via suppression of Dicer/let-7i-5p to induce epithelial-to-mesenchymal transition in colon cancer cells

Abstract Cancer cells reside in the hypoxic niches of tumors easily undergo epithelial-to-mesenchymal transition (EMT). We have recently shown that hypoxia-induced EMT to enhance colon cancer cell invasive growth is dependent on the orphan nuclear receptor Nur77 and is mediated by Akt signaling. However, its underlying molecular mechanisms remain elusive. Here we found that hypoxia-induced Nur77 reduced Akt phosphorylation and its downstream mediator mTOR by decreasing the mRNA stability of p110α, the catalytic subunit α of phosphatidylinositol 3-kinase. Further analyses revealed that this effect could be mediated by down-regulation of Dicer, an important microRNA (miR) processor, and decreased biogenesis of the miR, let-7i-5p. Luciferase reporter assays confirmed that let-7i-5p could directly target the 3’UTR of p110α mRNA. Knockdown of Dicer or overexpression of let-7i-5p inhibited Nur77-induced EMT phenotypes. These data uncover a novel mechanistic link connecting Nur77, Akt, and invasive properties of colon cancer in the hypoxic microenvironment. Citation Format: Sally K. Y. To, Shan Deng, Jin-Zhang Zeng, Alice Sze Tsai Wong. Hypoxia-induced Nur77 activates PI3K-p110a/Akt/mTOR via suppression of Dicer/let-7i-5p to induce epithelial-to-mesenchymal transition in colon cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4301.

PF806 SEPSIS INDUCED MRNA AND MIRNA LEVELS IN MEGAKARYOCYTES AND PLATELETS GENERATE ADVERSE PLATELET REACTIVITY

Background:In sepsis, platelet activation by lipopolysaccharide (LPS) via TLR4 can result in microvascular thrombosis. However, megakaryocytes (MKs) also express TLRs, thus severe infection can modulate thrombopoiesis. Both MKs and platelets are rich in microRNAs (miRNAs) to regulate messenger RNA (mRNA) function and different cellular events. Murine MKs were previously described to produce platelets with altered mRNA profile in septic mice.Aims:We characterized sepsis‐induced expression of mRNAs with their regulatory miRNAs in ex vivo and in vitro stimulated platelets as well as in MK cell cultures. The contribution of Dicer function to abnormal miRNA levels was also investigated.Methods:Leukocyte‐depleted platelets of 22 septic and 26 healthy individuals were analyzed for P2RY12 and SELP (P‐selectin) mRNAs. TaqMan Open Array was performed for miRNAs, and RT‐qPCR were used for verification. The effects of sepsis were also studied in isolated platelets and MEG‐01 cells in vitro after treatment with recombinant TNF‐α (100 ng/mL) or LPS (O55:B5, 100 ng/mL) with lipoprotein binding protein (100 ng/mL) and soluble CD14 (150 ng/mL) for 1–24 h. Dicer level was observed by western blotting and fluorescence microscope, while its function was tested by calpain inhibitor (calpeptin, 10 μmol/L) in septic MKs and silencing by Dicer siRNA (40 pmol) in MEG‐01 cells in comparison to control samples with NEG‐01 siRNA for P2RY12 and SELP expression. To prove the effect of LPS, TLR4 expression was observed on platelets and MKs by flow cytometry. Induced inflammatory conditions were evaluated by miR‐155 expression and IL‐1β/IL‐6 mRNA levels by RT‐qPCR and via nuclear translocation of p65 subunit of NF‐κB pathway by fluorescence microscope.Results:There was augmented platelet activation as surface and soluble P‐selectin were increased in septic patients (P < 0.001). Platelets and MKs upregulated P2RY12 and SELP gene expression (P < 0.01) accompanied with elevated inflammation‐specific miR‐155 and decreased miR‐223/26b. Additionally, 64 other platelet miRNAs (e.g. miR‐150, let‐7e) indicated ≥2‐fold decrease, while 37 (e.g. miR‐191) were increased at the same degree in sepsis vs. controls. Septic conditions resulted in substantial p65 translocation into nuclei causing at least 2‐fold elevated miR‐155 and IL‐1β or IL‐6 mRNA levels (P < 0.05) in platelets and MKs in the ex vivo and in vitro experiments via TLR4 receptors that could be detected on the surface of platelets (3–7%) and MEG‐01 cells (8–12%). After a transient induction of Dicer and miRNAs at 1 h, reduced Dicer mRNA and protein levels were seen in LPS/TNF‐α treated platelets/MKs after 4–24 h causing attenuated miR‐223/26b. Calpain inhibition restored miRNA levels, while downregulation of Dicer generated higher P2RY12 and SELP levels in MEG‐01.Summary/Conclusion:Alteration in Dicer‐dependent miRNAs contribute to elevated mRNA levels in MKs and reactive platelets during sepsis.This study is supported by the GINOP‐2.3.2–15–2016–00043‐IRONHEART project.

Dual mechanism of DICER downregulation facilitates cancer metastasis

ABSTRACTAlthough downregulation of DICER – a critical enzyme in microRNA (miRNA) maturation – reportedly promotes cancer metastasis, understanding of its upstream regulators remains limited. Our recent study demonstrated a noncanonical oncogenic effect of hypoxia-inducible factor-1α (HIF-1α), which directly binds with DICER to promote PARKIN-mediated autophagic–lysosomal proteolysis and consequently suppresses miRNA biogenesis, facilitating metastasis.

Abstract B59: Role of Dicer on human melanoma progression and resistance

Abstract Melanoma is a serious public health problem that affects the population of Latin America and is increasing rapidly compared to other types of tumors. The growth or change in this type of tumor is progressive and is in the horizontal and/or vertical direction. Breslow thickness (vertical staging) is the tumor thickness in the dermis where patients with lesion thickness less than 0.75 mm have good prognosis, unlike lesion thickness larger than 3 mm. This stage is classified into T (primary tumor): T0 (with no evidence of primary tumor); Tis (in situ melanoma); T1 (1 mm); T2 (1.01 to 2 mm); T3 (2.01 to 4 mm); and T4 (above 4 mm). Knowing some molecular markers of melanoma is essential for the identification of genetically predisposed individuals, as well as early detection of the disease. Recent works has demonstrated that microRNAs may be involved in modulation of melanoma. Dicer is an essential member of the RNase III family which controls maturation of miRNAs in the cytoplasm from microRNA precursors (pre-miRNAs). The upregulation of Dicer is associated with aggressive features and proliferation of melanoma and no other skin tumors such as carcinomas and sarcoma. In our present study, we found that the knockdown expression of Dicer using the CRISPR/CAS9 in melanoma cell line induced more chemosensitivity to cisplatin and these changes correlated with the downregulation of Dicer. We examined the consequence of Dicer knockdown on melanoma cell proliferation, clonogenic assays, and overall survival. We also compared Dicer in tissue from patients diagnosed with melanoma in different stages with the prognosis of these patients, suggesting that the reduction in Dicer expression is associated with melanoma progression. Considering the fundamental and multiple biologic roles of Dicer in various cellular processes, our results suggest that modulation of Dicer in melanoma should become a promising therapeutic candidate for further clinical application. Note: This abstract was not presented at the conference. Citation Format: Nathalia Cruz de Victo, Sandy Adjemian, Romulo dos Santos Sobreira Nunes, Rildo Aparecido Volpini, Mara Huffenbaecher Giavina-Bianchi, Cyro Festa Neto, Niels Olsen Saraiva Câmara, Gustavo Pessini Amarante-Mendes, Jacqueline de Fátima Jacysyn. Role of Dicer on human melanoma progression and resistance [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr B59.

Hypoxia Causes Downregulation of Dicer in Hepatocellular Carcinoma, Which Is Required for Upregulation of Hypoxia-Inducible Factor 1α and Epithelial-Mesenchymal Transition.

Purpose: A role of Dicer, which converts precursor miRNAs to mature miRNAs, in the tumor-promoting effect of hypoxia is currently emerging in some tumor entities. Its role in hepatocellular carcinoma (HCC) is unknown.Experimental Design: HepG2 and Huh-7 cells were stably transfected with an inducible Dicer expression vector and were exposed to hypoxia/normoxia. HepG2-Dicer xenografts were established in nude mice; hypoxic areas and Dicer were detected in HCC xenografts and HCCs from mice with endogenous hepatocarcinogenesis; and epithelial-mesenchymal transition (EMT) markers were analyzed by immunohistochemistry or by immunoblotting. The correlation between Dicer and carbonic anhydrase 9 (CA9), a marker of hypoxia, was investigated in resected human HCCs.Results: Hypoxia increased EMT markers in vitro and in vivo and led to a downregulation of Dicer in HCC cells. The levels of Dicer were downregulated in hypoxic tumor regions in mice with endogenous hepatocarcinogenesis and in HepG2 xenografts. In human HCCs, the levels of Dicer correlated inversely with those of CA9, indicating that the negative regulation of Dicer by hypoxia also applies to HCC patients. Forced expression of Dicer prevented the hypoxia-induced increase in hypoxia-inducible factor 1α (HIF1α), HIF2α, hypoxia-inducible genes (CA9, glucose transporter 1), EMT markers, and cell migration.Conclusions: We here identify downmodulation of Dicer as novel essential process in hypoxia-induced EMT in HCC and demonstrate that induced expression of Dicer counteracted hypoxia-induced EMT. Thus, targeting hypoxia-induced downmodulation of Dicer is a promising novel strategy to reduce HCC progression. Clin Cancer Res; 23(14); 3896-905. ©2017 AACR.

Hypoxia causes down-regulation of Dicer in hepatocellular carcinoma, which is required for up-regulation of hypoxia inducible factor 1α and epithelial-mesenchymal transition

Hypoxia causes down-regulation of Dicer in hepatocellular carcinoma, which is required for up-regulation of hypoxia inducible factor 1α and epithelial-mesenchymal transition

Dicer suppresses the malignant phenotype in VHL-deficient clear cell renal cell carcinoma by inhibiting HIF-2α.

Both the von Hippel-Lindau (VHL)/hypoxia-inducible factor (HIF) pathway and microRNA (miRNA) regulation are important mechanisms underlying the development and progression of clear cell renal cell carcinoma (ccRCC). Here we demonstrate that VHL deficiency leads to downregulation of Dicer and, in turn, defects in the miRNA biogenesis machinery in ccRCCs. Dicer inhibited expression of HIF-2α, which was a direct target of Dicer-dependent miR-182-5p in VHL-deficient ccRCCs. Ectopic Dicer expression in VHL-deficient ccRCCs suppressed tumor growth and angiogenesis by inhibiting HIF-2α both in vitro and in vivo. Reduced Dicer mRNA levels served as an independent prognostic factor for poor survival in patients with VHL-deficient ccRCC. Our results indicate that downregulation of Dicer in VHL-deficient ccRCCs contributes to high levels of HIF-2α and a malignant phenotype, which suggests Dicer could be a useful therapeutic target for managing this disease.

Possible involvement of miRNAs in tropism of Parvovirus B19.

Human Parvovirus B19 (PVB19) is one of the most important pathogens that targets erythroid lineage. Many factors were mentioned for restriction to erythroid progenitor cells (EPCs). Previous studies showed that in non-permissive cells VP1 and VP2 (structural proteins) mRNAs were detected but could not translate to proteins. A bioinformatics study showed that this inhibition might be due to specific microRNAs (miRNAs) present in non-permissive cells but not in permissive EPCs. To confirm the hypothesis, we evaluated the effect of miRNAs on VP expression. CD34(+) HSCs were separated from cord blood. Then, CD34(+) cells were treated with differentiation medium to obtain CD36(+) EPCs. To evaluate the effect of miRNAs on VP expression in MCF7 and HEK-293 cell lines (non-permissive cells) and CD36(+) EPCs, dual luciferase assay was performed in presence of shRNAs against Dicer and Drosha to disrupt miRNA biogenesis. QRT-PCR was performed to check down-regulation of Dicer and Drosha after transfection. All measurements were done in triplicate. Data means were compared using one-way ANOVAs. MicroRNA prediction was done by the online microRNA prediction tools. No significant difference was shown in luciferase activity of CD36(+) EPCs after co-transfection with shRNAs, while it was significant in non-permissive cells. Our study revealed that miRNAs may be involved in inhibition of VP expression in non-permissive cells, although further studies are required to demonstrate which miRNAs exactly are involved in regulation of PVB19 replication.

Dysfunctional Subcutaneous Fat With Reduced Dicer and Brown Adipose Tissue Gene Expression in HIV-Infected Patients.

HIV patients are at an increased risk for cardiometabolic disease secondary to depot-specific alterations in adipose function, but mechanisms remain poorly understood. The endoribonuclease Dicer has been linked to the modulation of brown and white adipocyte differentiation. We previously demonstrated that Dicer knockout mice undergo transformation of brown adipose tissue to white adipose tissue and develop a lipodystrophic phenotype. We hypothesized reduced Dicer and brown adipose tissue gene expression from nonlipomatous sc fat among HIV patients with a lipodystrophic phenotype. Eighteen HIV (nine with and without lipodystrophic changes in fat distribution, characterized by excess dorsocervical adipose tissue [DCAT]) and nine non-HIV subjects underwent punch biopsy of abdominal sc fat to determine expression of Dicer and other adipose-related genes. HIV subjects with long-duration antiretroviral use demonstrated excess DCAT vs non-HIV subjects (9.8 ± 1.0 vs 6.6 ± 0.8 cm(2), P = .02) with similar body mass index. Dicer expression was decreased in abdominal sc fat of HIV vs non-HIV (4.88 [1.91, 11.93] vs 17.69 [10.72, 47.91], P = .01), as were PPARα, ZIC1, PRDM16, DIO2, and HSP60 (all P ≤ .03). Moreover, the expression of Dicer (2.49 [0.02, 4.88] vs 11.20 [4.83, 21.45], P = .006), brown fat (PPARα [P = .002], ZIC1 [P = .004], LHX8 [P = .03], PRDM16 [P = .0008], PAT2 [P = .008], P2RX5 [P = .02]), beige fat (TMEM26 [P = .004], CD137 [P = .008]), and other genes (DIO2 [P = .002], leptin [P = .003], HSP60 [P = .0004]) was further decreased in abdominal sc fat comparing HIV subjects with vs without excess DCAT. Down-regulation of Dicer in the abdominal sc fat correlated with the down-regulation of all brown and beige fat genes (all P ≤ .01). Our results demonstrate dysfunctional sc adipose tissue marked by reduced Dicer in relationship to the down-regulation of brown and beige fat-related genes in lipodystrophic HIV patients and may provide a novel mechanism for metabolic dysregulation. A strategy to increase browning of white adipose tissue may improve cardiometabolic health in HIV.

Abstract 199: Functional mechanism of hypoxia-inducible factor 1 alpha-mediated Dicer down-regulation

Abstract MicroRNAs (miRNAs) are generated by a multiple steps process that post-transcriptionally regulate the expression of target genes. Dysregulation of miRNAs is linked to human diseases including the development of human cancer. Abrogation of cellular global miRNAs maturation has been proposed to promote tumorigenesis and cancer metastasis. Hypoxia stress is the major cause of dysregulation of miRNAs and promotes tumor angiogenesis, metastasis and tumorigenesis which is a pivotal factor to switch on the cellular oncogenic features during tumor progression. Although hypoxia stress regulates expression of a subset of miRNAs, the upstream regulators controlling miRNAs regulation under hypoxia remain unclear. This study demonstrates the molecular mechanism of post-translational regulation of Dicer under hypoxia. Our results show that knockdown of hypoxia inducible factor 1 alpha (HIF-1α) up-regulates Dicer expression in colorectal cancer (CRC) cells. Overexpression of HIF-1α enhances ubiquitination of Dicer and subsequently promotes it recognition by autophagic receptor for autophagy-lysosomal degradation. We also find that HIF-1α enhances cancer cell migration by regulating Dicer-regulated miRNAs. In conclusion, we demonstrated that HIF-1α down-regulated Dicer and abolishes miRNA biogenesis to enhance cancer cell migration. This study may provide a potential therapeutic direction that targets the dysregulated miRNAs in tumor hypoxia for patients with poor prognosis and metastatic CRC. Citation Format: Hui-Huang Lai, Yu-Jhen Lyu, Jie-Ning Li, Jen-Liang Su, Pai-Sheng Chen. Functional mechanism of hypoxia-inducible factor 1 alpha-mediated Dicer down-regulation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 199. doi:10.1158/1538-7445.AM2015-199

Ablation of Dicer leads to widespread perturbation of signaling pathways

Dicer is an essential ribonuclease involved in the biogenesis of miRNAs. Previous studies have reported downregulation of Dicer in multiple cancers including hepatocellular carcinoma. To identify signaling pathways that are altered upon Dicer depletion, we carried out quantitative phosphotyrosine profiling of liver tissue from Dicer knockout mice. We employed antibody-based enrichment of phosphotyrosine containing peptides coupled with SILAC spike-in approach for quantitation. High resolution mass spectrometry-based analysis identified 349 phosphotyrosine peptides corresponding to 306 unique phosphosites of which 75 were hyperphosphorylated and 78 were hypophosphorylated. Several receptor tyrosine kinases including MET, PDGF receptor alpha, Insulin-like growth factor 1 and Insulin receptor as well as non-receptor tyrosine kinases such as Src family kinases were found to be hyperphosphorylated upon depletion of Dicer. In addition, signaling molecules such as IRS-2 and STAT3 were hyperphosphorylated. Activation of these signaling pathways has been implicated previously in various types of cancers. Interestingly, we observed hypophosphorylation of molecules including focal adhesion kinase and paxillin. Our study profiles the perturbed signaling pathways in response to dysregulated miRNAs resulting from depletion of Dicer. Our findings warrant further studies to investigate oncogenic effects of downregulation of Dicer in cancers.

Reduction of protein kinase C α (PKC-α) promote apoptosis via down-regulation of Dicer in bladder cancer.

In clinic, we examined the expression of protein kinase C (PKC)-α and Dicer in the samples of bladder cancer patients, and found that the two proteins have a line correlation. Our study confirmed this correlation existing by clearing the decreasing expression of Dicer after the PKC-α knockdown. Treatment of bladder cancer cell lines (T24, 5637) with the PKC-α or Dicer knockdown and the PKC inhibitors (Calphostin C and Gö 6976) can promote the apoptosis. Inhibition of PKC can increase the activities of caspase-3 and PARP, however, decrease the expression of Dicer. And knockdown of the PKC-α or Dicer can also activate the caspase-3 or the PARP. Considering the reduction of PKC-α can induce the Dicer down-regulation, we make the conclusion that the reduction of PKC-α can promote the apoptosis via the down-regulation of Dicer in bladder cancer.

Dicer expression and microRNA dysregulation associate with aggressive features in thyroid cancer

Altered miRNA expression and down-regulation of Dicer has been shown in various cancers. We investigated Dicer expression and global miRNA environment in correlation with malignant features of thyroid tumors. Dicer gene expression was assessed for 22 normal thyroids, 16 follicular adenomas, 28 papillary thyroid cancers (PTCs), 10 tall-cell variants of PTC, 11 follicular variants of PTC, as well as the four thyroid cell lines BCPAP, TPC1, KTC1, and TAD2 via quantitative polymerase chain reaction. BRAF((V600E)) mutation screening was completed for 31 neoplasms. Next-generation sequencing was performed on a subset of PTC and normal thyroid. Protein levels were assessed via Western blotting and immunohistochemistry. Dicer mRNA was down-regulated in malignant thyroid samples and cell lines compared with normal tissues, benign neoplasms, and the fetal cell line TAD2. Decreased Dicer gene expression in malignant tissues was correlated greatly with aggressive features: extrathyroidal extension, angiolymphatic invasion, multifocality, lymph node and distant metastasis, recurrence, and BRAF((V600E)) mutation. Conversely, increased levels of Dicer protein were observed in malignant tissues and cell lines. Sequencing yielded 19 differentially expressed miRNAs. Eight samples had a nonsignificant a global down-regulation in malignant tissues. Dysregulation of Dicer and possibly altered expression of miRNAs are associated with aggressive features in thyroid cancers. These findings suggest that disruption in normal miRNA processing involving Dicer may play a role in thyroid cancer progression.

Abstract 3532: Hypoxia is a master regulator of Drosha- and Dicer-dependent miRNA biogenesis in cancer

Abstract Background: Drosha and Dicer are 2 key enzymes involved in miRNA biogenesis. Individual regulators of Dicer (e.g let7) have been implicated, but the underlying mechanisms are currently poorly understood. Here, we identified new mechanisms of deregulation of miRNA biogenesis in tumor cells, whereby hypoxia causes reduction in Drosha and Dicer. Methods and Results: Differential levels of Drosha and Dicer was found between tumor samples and their expression correlated negatively with CA9, a hypoxia marker (Drosha vs. CA9 r=-0.65, Dicer vs. CA9 r=-0.69; p<0.05). We further found that Drosha and Dicer are down-regulated by >70% in hypoxic compared to normoxic conditions across a panel of ovarian and breast cancer cell lines and microdisected tumor tissues. Analysis of TCGA data showed that the expressions of Drosha and Dicer or hypoxia are independent predictors of poor patient survival. Furthermore, RNA-sequencing and mature miRNA array analyses both revealed a significant disruption in miRNA maturation when cells were exposed to hypoxia. Through ChIP assays and promoter reporter studies, we found that ETS1 and ELK1 are responsible for transcriptionally repressing Drosha expression under hypoxia by binding to its promoter region. We further show that ETS1/ELK1 recruit ARID5B and HDAC1 to methylate Drosha promoter. In contrast to Drosha, Dicer level is altered post-transcriptionally under hypoxia. Several miRNAs that are up-regulated under hypoxia are predicted to target Dicer. By transfecting tumor cells with miRNA mimics or anti-miR constructs along with 3′ UTR luciferase assays, we showed that miR-630 is a strong regulator of Dicer in hypoxic conditions. Bioinformatics analysis of downregulated miRNAs and their gene targets from RNA-seq data identified novel miRNA (let7a, miR-30c, miR-135a, miR-146a)-mRNA (RHOB, TAGLN, JUN, CTGF, SERTAD, TXNIP, JAG1) interactions aiding metastasis under hypoxia. Given the potential for anti-VEGF therapies in inducing significant hypoxia in tumors, we examined the biological effects of anti-miR-630 or siETS1/ELK1 in orthotopic ovarian and breast cancer mouse models. We first demonstrated that in vivo tumor samples treated with anti-VEGF therapy results in significant Drosha and Dicer down-regulation. ETS1+ELK1siRNA or anti-miR630 DOPC nanoparticles in vivo rescued Drosha and Dicer expression under anti-VEGF therapy, resulting in a significant reduction in cancer metastasis (p<0.05). Conclusion: In summary, these findings provide new insights into the mechanisms underlying Drosha and Dicer downregulation following hypoxia and resultant effects on cancer metastasis. Citation Format: Rajesha Rupaimoole, Cristina Ivan, Chad Pecot, Sherry Wu, Sunila Pradeep, Behrouz Zand, Archana Nagaraja, Kshipra Gharpure, Heather Dalton, Nouara Sadaoui, Wei Zhang, Gabriel Lopez-Berestein, Anil Sood. Hypoxia is a master regulator of Drosha- and Dicer-dependent miRNA biogenesis in cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3532. doi:10.1158/1538-7445.AM2014-3532

Down-regulation of Dicer and Ago2 is associated with cell proliferation and apoptosis in prostate cancer.

Dicer and Argonaute2 (Ago2) are critical components responsible not only for RNA interference but also for microRNA synthesis. The present study investigated the roles of Dicer and Ago2 in prostate cancer (Pca). First, the expression levels of Dicer and Ago2 in Pca tissues were determined by immunohistochemistry (IHC) and compared with pathological features. Next, RNA interference was used to down-regulate the expression levels of Dicer and Ago2 in the Pca cell lines LNCaP, PC-3, and DU145, and effects on proliferation, apoptosis, and cell cycle were detected using the CCK-8 assay and flow cytometry, respectively. We found that Dicer and Ago2 expression levels in Pca tissues were higher than those in adjacent benign tissues and correlated with lower Gleason patterns, with the exception of Dicer expression in localized Pca. In vitro, silencing Dicer or Ago2 inhibited cell proliferation and induced apoptosis in LNCaP, PC-3, and DU145, as well as arrested the cell cycle at the G2/M phase in androgen-dependent LNCaP, or at S phase in the androgen-independent PC-3 and DU145. Altogether these findings suggest that Dicer and Ago2 play important roles in proliferation, apoptosis, and the cell cycle in Pca and might serve as both promising biomarkers for Pca progression and potential therapeutic targets.